A 28-patient phase 1 gene therapy clinical trial for the degenerative retinal disease Leber hereditary optic neuropathy (LHON) found no significant safety concerns; however, treatment failed to improve or slow vision loss, with even the highest dose. LHON affects the optic nerve, which carries visual signals from the light-sensing retina to the brain. The study, published in the American Journal of Ophthalmology, was sponsored in part by the National Eye Institute, a part of the National Institutes of Health.